It is desired to acquire images of real-world 3D scenes and display them as realistic 3D images. Automultiscopic displays offer uninhibited viewing, i.e., without glasses, of high-resolution stereoscopic images from arbitrary positions in a viewing zone. Automultiscopic displays include view-dependent pixels with different intensities and colors based on the viewing angle. View-dependent pixels can be implemented using conventional high-resolution displays and parallax-barriers.
In a typical automultiscopic display, images are projected through a parallax-barrier, onto a lenticular sheet, or onto an integral lens sheet. The optical principles of multiview auto-stereoscopy have been known for over a century, Okoshi, Three-Dimensional Imaging Techniques, Academic Press, 1976. Practical displays with a high resolution have recently become available. As a result, 3D television is receiving renewed attention.
However, automultiscopic displays have several problems. First, a moving viewer sees disturbing visual artifacts. Secondly, the acquisition of artifact-free 3D images is difficult. Photographers, videographers, and professionals in the broadcast and movie industry are unfamiliar with the complex setup required to record 3D images. There are currently no guidelines or standards for multi-camera parameters, placement, and post-production processing, as there are for conventional 2D television.
In particular, the pixels in the image sensor of the camera, do not map directly to pixels in the display device, in a one-to-one manner, in most practical cases. This requires resampling of the image data. The resampling needs to be done in such a way that visual artifacts are minimized. There is no prior art for effective resampling of light fields for automultiscopic displays.
Most prior art anti-aliasing for 3D displays uses wave optics. Furthermore, those methods require scene depth on a per pixel basis for appropriate filtering. In the absence of depth information, the methods resort to a conservative worst case approach and filter based on a maximum depth in the scene. In practice, this limits implementations to scenes with very shallow depths.
Generally, automultiscopic displays emit static or time-varying light fields. A light field represents radiance as a function of position and direction in regions of space free of occluders. A frequency analysis of light fields is done using a plenoptic sampling theory. There, the spectrum of a scene is analyzed as a function of object depth. This reveals that most light fields are aliased. A reconstruction filter can be applied to remove aliasing and to preserve, as much as possible, the original spectrum.
Re-parameterization can be used to display light fields on automultiscopic displays. However, reparameterization does not address display aliasing. The reconstruction filter can be enhanced with a wide aperture filter. This can produce 3D images with a larger depth of field without sacrificing the sharpness on the focal plane.
While display quality is one critical issue in a 3D rendering system, the amount of data that need to be processed, rendered, and transmitted to such displays must also be considered. Because the light field data are at least an order of magnitude larger than for systems based on stereo-image pairs, data compression processes are needed. It is particularly important that transmission bandwidth be reduced and that decoding resources in the receiver be kept to a minimum.
None of the prior art methods deal with sampling and anti-aliasing for automultiscopic displays. They do not take into account the sampling rate of the display, and only consider the problem of removing aliasing from sampled light fields during reconstruction. Furthermore, none of the prior art methods employ sampling and anti-aliasing in the context of a compression system or method.